Small antenna apparatus and method for controlling the same

ABSTRACT

An antenna apparatus for a mobile terminal is provided. The antenna apparatus includes an antenna pattern, a first electric circuit and a second electric circuit respectively connected between both ends of the antenna pattern and a system ground, and a third electric circuit disposed between the antenna pattern and a feeding line, wherein the first electric circuit and the second electric circuit extend electrical wavelengths of the antenna pattern and the third electric circuit increases input impedance matching.

PRIORITY

This application claims the benefit under 35 U.S.C. §119(a) of a Koreanpatent application filed on Jan. 13, 2012 in the Korean IntellectualProperty Office and assigned Ser. No. 10-2012-0004448, the entiredisclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to small antenna technology using circuitresonance instead of wave resonance by using a predetermined patternthat may be printed or made of an iron structure, or any other suitablematerial, printed on a Printed Circuit Board (PCB) and/or formed on atool such as a carrier and an electric circuit connected thereto inorder to decrease a spatial constraint and a cost and shorten adevelopment period in a mobile terminal supporting various additionalfunctions such as Global Positioning Service (GPS), Bluetooth (BT),WiFi, and other similar and/or suitable functions.

2. Description of the Related Art

Generally, a mobile terminal may include various kinds of wirelesscommunication units in order to perform wireless communicationfunctions. In addition, the wireless communication units may perform thewireless communication functions using an antenna corresponding thereto.Currently, the mobile terminal may include a communication unit such asa Long Term Evolution (LTE) communication unit, a Wideband Code DivisionMultiple Access (WCDMA), and any other similar and/or suitable type ofcommunication unit, for wireless communication with a base station, acommunication unit such as a WiFi communication unit, a WirelessBroadband (Wibro) communication unit, a Worldwide Interoperability forMicrowave Access (Wimax) communication unit, and any other similarand/or suitable type of communication unit, for connection with theInternet network, a communication unit such as a Bluetooth communicationunit, a Near-Field Communication (NFC) unit, and any other similarand/or suitable type of communication unit, for near fieldcommunications and/or short range communications, a GPS receiving unit,and any other similar and/or suitable communication unit. Thecommunication units as described above may include antennas forperforming the wireless communication using Radio Frequency (RF)communication with objects external to the mobile terminal. That is, thecurrent mobile terminal may include a plurality of antennas forperforming the wireless communication functions. Therefore, the antennashould be miniaturized and/or have a small size thereof in order tomount the plurality of antennas to the mobile terminal.

A Planar Inverted F Antenna (PIFA) is a type of a small antenna. In thecase of the PIFA type used in the mobile terminal, ¼ wavelength ofusable frequency is needed. For example, in the case of a GPS antenna,which has a frequency band of 1.575 GHz, a physical length of 4.7 cm inthe air is needed, and in the case of an LTE antenna, which has afrequency band of 700 MHz band, a physical length of 10.7 cm in the airis needed. Therefore, since the mobile terminal of the related artshould support various wireless communication functions including theplurality of antennas, there is a problem that the plurality of antennasmay occupy a significant space of the mobile terminal. Accordingly,there is a limitation in manufacturing mobile terminals having aplurality of antennas and a small size. In addition, since resonance ofthe antenna may be determined by the physical length of the antenna, alonger amount of time may be needed for tuning at the time ofmanufacturing design and development steps, such as a modification of amold and the like.

Therefore, a need exists for a system and method for small antennatechnology using circuit resonance instead of wave resonance.

The above information is presented as background information only toassist with an understanding of the present disclosure. No determinationhas been made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the present invention.

SUMMARY OF THE INVENTION

Aspects of the present invention are to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentinvention is to provide a small antenna apparatus using circuitresonance instead of wave resonance by connecting an electric circuit tothe antenna apparatus. Here, the small antenna may be a metal structurehaving a predetermined pattern printed on a Printed Circuit Board (PCB)or formed on a tool such as a carrier.

Another aspect of the present invention is to provide a small antennaapparatus that uses an electric circuit, such as a lumped element, aninter-digital circuit, or the like, positioned on the PCB at both endsof an asymmetrical antenna pattern implemented on the PCB or at bothends of an asymmetrical antenna pattern attached to the tool and afeeding line, thereby increasing both of an electrical wavelength and aninput impedance matching.

In accordance with an aspect of the present invention, an antennaapparatus is provided. The apparatus includes an antenna pattern, afirst electric circuit and a second electric circuit respectivelyconnected between both ends of the antenna pattern and a system ground,and a third electric circuit disposed between the antenna pattern and afeeding line, wherein the first electric circuit, the second electriccircuit, and the third electric circuit extend electrical wavelengths ofthe antenna pattern in order to increase input impedance matching.

In accordance with another aspect of the present invention, a mobileterminal is provided. The mobile terminal includes an antenna apparatusincluding an antenna pattern, a first electric circuit and a secondelectric circuit respectively connected between both ends of the antennapattern and a system ground, and a third electric circuit disposedbetween the antenna pattern and the feeding line, a communication unitfor receiving a Radio Frequency (RF) parameter from a base station, amemory for storing a reference RF parameter therein; and a control unitfor comparing the received RF parameter with the reference RF parameterand for changing a device value of a corresponding electric circuit,from among the first electric circuit, the second electric circuit andthe third electric circuit of the antenna apparatus until a change valuebetween the received RF parameter and the reference RF parametersatisfies a reference RF parameter when the comparison value is out ofthe reference RF parameter.

In accordance with another aspect of the present invention, a mobileterminal is provided. The mobile terminal includes an antenna apparatusincluding a antenna pattern, a first electric circuit and a secondelectric circuit respectively connected between both ends of the antennapattern and a system ground, and a third electric circuit disposedbetween the antenna pattern and a feeding line, a memory for storing areference RF parameter therein, and a control unit for measuring an RFparameter which is outputted from the antenna apparatus, for comparingthe measured RF parameter with the reference RF parameter and forchanging the device value of the electric circuit, from among the firstelectric circuit, the second electric circuit and the third electriccircuit, of the antenna apparatus until a comparison value between themeasured RF parameter and the reference RF parameter satisfies areference specification when the comparison value is out of thereference specification.

In accordance with another aspect of the present invention, a method forcontrolling the resonance frequency of an antenna apparatus of a mobileterminal is provided. The method includes receiving an RF parameter froma base station, comparing the received RF parameter with a reference RFparameter stored in a memory of the mobile terminal, and changing thedevice value of a corresponding electric circuit of an antenna apparatusuntil a comparison value between the received RF parameter and thereference RF parameter satisfies a reference specification when thecomparison value is not the reference specification. The antennaapparatus includes an antenna pattern, a first electric circuit and asecond electric circuit respectively connected between both ends of theantenna pattern and a system ground, and a third electric circuitdisposed between the antenna pattern and a feeding line.

In accordance with another aspect of the present invention, a method forcontrolling a resonance frequency of an antenna of a mobile terminal isprovided. The method includes measuring a output of an antenna apparatusincluding an antenna pattern, a first electric circuit and a secondelectric circuit respectively connected between both ends of the antennapattern and a system ground, and a third electric circuit disposedbetween the antenna pattern and a feeding line, comparing the measuredRF parameter with a reference RF parameter stored in a memory, andchanging the device value of a corresponding electric circuit of theantenna apparatus until a comparison value between the measured RFparameter and the reference RF parameter satisfies a referencespecification when the comparison value is not the referencespecification.

Other aspects, advantages, and salient features of the invention willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainexemplary embodiments the present invention will be more apparent fromthe following detailed description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a diagram illustrating a structure of a small antennaaccording to an exemplary embodiment of the present invention, andillustrating a structure of a small antenna printed on a Printed CircuitBoard (PCB);

FIG. 2 is diagram illustrating a configuration of an equivalent circuitof a small antenna having a configuration such as the configurationshown in FIG. 1 according to an exemplary embodiment of the presentinvention;

FIG. 3 is a diagram illustrating a flow of current in an antenna at atime of resonance generation in a small antenna apparatus according toan exemplary embodiment of the present invention;

FIG. 4 is a diagram illustrating a structure of a small antenna havinganother structure printed on a PCB according to an exemplary embodimentof the present invention;

FIG. 5 is a diagram illustrating a structure of a small antenna having aconfiguration of an antenna apparatus when an antenna is attached to aspecific tool of a mobile terminal according to an exemplary embodimentof the present invention;

FIG. 6 is a diagram illustrating a small antenna apparatus in whichinput impedance and a length of an antenna are matched to each other byconnecting an electric circuit to both ends and a feeding ends of theantenna according to an exemplary embodiment of the present invention;

FIGS. 7A and 7B are diagrams illustrating change characteristics of aresonance point due to a change of an electric circuit connected to bothends of an antenna in an antenna apparatus having a structure such asthat shown in FIG. 6 according to an exemplary embodiment of the presentinvention;

FIG. 8 is a diagram illustrating change characteristics of return lossdue to a change of an electric circuit connected to a feeding point ofan antenna apparatus having a structure such as that shown in FIG. 6according to an exemplary embodiment of the present invention;

FIG. 9 is a diagram illustrating a configuration of changing an electriccircuit in an antenna apparatus according to an exemplary embodiment ofthe present invention;

FIG. 10 is a flowchart illustrating a procedure of changing an electriccircuit of an antenna apparatus such as that shown in FIG. 9 accordingto an exemplary embodiment of the present invention;

FIG. 11 is a diagram illustrating a configuration of a mobile terminalhaving a small antenna apparatus according to an exemplary embodiment ofthe present invention; and

FIG. 12 is a flowchart illustrating a procedure of changing a resonancefrequency of an antenna apparatus in a mobile terminal according to anexemplary embodiment of the present invention.

Throughout the drawings, it should be noted that like reference numbersare used to depict the same or similar elements, features, andstructures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of exemplaryembodiments of the invention as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the embodiments described hereincan be made without departing from the scope and spirit of theinvention. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of theinvention. Accordingly, it should be apparent to those skilled in theart that the following description of exemplary embodiments of thepresent invention is provided for illustration purpose only and not forthe purpose of limiting the invention as defined by the appended claimsand their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

The present invention relates to a small antenna apparatus that may beused in a mobile terminal supporting various wireless communicationfunctions such as Long Term Evolution (LTE), Global Positioning Service(GPS), Bluetooth (BT), WiFi, and other similar and/or suitable wirelesscommunication services. The small antenna apparatus, according to anexemplary embodiment of the present invention, has a structureconnecting an electric circuit to both ends and/or a feeding point of apredetermined pattern which may be printed and/or may be made of an ironstructure or any suitable and/or similar material, formed on a tool suchas a carrier or printed on a Printed Circuit Board (PCB), and may use acircuit resonance instead of a wave resonance.

The small antenna apparatus, according to an exemplary embodiment of thepresent invention, may use an electric circuit, such as a lumpedelement, an inter-digital circuit, and any other similar and/or suitableelectric circuit, positioned on the PCB of the mobile terminal for bothends of an antenna pattern and/or feeding line, such that an electricalwavelength and an input impedance are simultaneously improved, therebymaking it possible to save approximately 50% of a space used by thesmall antenna apparatus of the exemplary embodiment of the presentinvention, as compared to a small antenna of the related art. Inaddition, tuning of a resonance point of the antenna may be performedthrough the electric circuit connected to the antenna pattern, such thatit may be unnecessary to spend time for generating a mold modificationtime during design and development of the small antenna apparatusaccording to an exemplary embodiment of the present invention, therebymaking it possible to reduce a development time. In the small antennaapparatus according to an exemplary embodiment of the present invention,the feeding line may be connected to the antenna pattern through theinter-digital circuit instead of the lumped element that may generateunnecessary resonance, such that the input impedance may be increasedand a tolerance of the existing lumped element may be reduced. Theantenna pattern of the small antenna apparatus, according to anexemplary embodiment of the present invention, may be an asymmetricalantenna pattern implemented on the PCB or may be the asymmetricalantenna pattern attached to a tool.

As described above, the small antenna apparatus, according to anexemplary embodiment of the present invention, may have a structure inwhich an electric circuit may be connected to both ends of the antennapattern and/or the feeding line to which signal is supplied. The antennapattern may be an antenna pattern implemented on the PCB or an antennapattern of the metal material attached to the tool. Further, the antennapattern may be asymmetrically formed based on the feeding line in orderto provide a degree of freedom in mounting. In addition, the electriccircuit may be a circuit made of a combination of resistance R, inductorL, and capacitor C that is a passive device generating electricalresonance and may be a circuit made of a combination of at least one ofa Field Effect Transistor (FET), a Bipolar Junction Transistor (BJT),and a diode that is an active device, and may be a circuit made of acombination of the passive device and the active device. The electricdevice may have a chip type or a package type and may be implemented asthe inter-digital structure implemented on the PCB.

FIG. 1 is a diagram illustrating a structure of a small antennaaccording to an exemplary embodiment of the present invention,illustrating a structure of a small antenna printed on a PCB.

Referring to FIG. 1 the structure of the antenna apparatus may beillustrated such that a ground plane is not shown. Electric circuits 120and 130 are connected to the both ends of an antenna 110 and theelectric circuits 120 and 130 are connected to a PCB 150. A feeding lineconnected to a Feeding Point (FP) is connected to the antenna 110through an electric circuit 140. Here, the electric circuit 120 isconnected to a shorting point and the electric circuit 130 is connectedto a radiation point. The small antenna having the above-mentionedconfiguration may be a PIFA type of antenna.

The Planar Inverted F Antenna (PIFA) is an antenna that may beimplemented with a small size and may be embedded in the mobileterminal. As shown in FIG. 1, the PIFA may be configured to include thePCB 150 which may also be referred to as a radiation PCB 150, theantenna 110, which is a conductor printed on the PCB 150, the feedingline connected to the antenna 110 through the electric circuit 140, theelectric circuits 120 and 130 connected from the both ends of theantenna 110 to the system ground (not shown) of the PCB 150. An entiretyof the shape of the PIFA may have a form of the letter F. The PIFA maycover a bandwidth for a variety of mobile communication bands, such as3^(rd) Generation (3G) and 4^(th) Generation (4G) communication bands,and any additional communication bands for features such as GPS, WiFi,Bluetooth, and the like.

When the current supplied from the PCB 150 is applied to the FP in thePIFA, as described above, the current may be transferred to the antenna110 through the feeding line and may be radiated through the antenna 110and electric circuits 120 and 130. Here, the antenna apparatus may forma transmission line formed of the antenna 110, the electric circuit 130,the system ground of the PCB 150 and the electric circuit 120 by thecurrent supplied from the FP. The antenna 110 and the electric circuits120 and 130 may receive radio waves, such as Radio Frequency (RF)signals, in the air or may radiate the radio waves into the air due tothe transmission line circulated as described above.

Main elements of the PIFA performing the above-mentioned configurationand operation may be related to bandwidth, a return loss in a resonancefrequency, impedance matching efficiency, and the like. At this time,the resonance frequency of the antenna apparatus having a configurationaccording to the present exemplary embodiment may be affected by aphysical length of the antenna 110. A resonance may be generated in aspecific frequency by the length of the antenna 110. Here, since theresonance of the antenna 110 may be determined by the physical length ofthe antenna 110, when the resonance frequency is to be changed, thechange may be implemented by tuning the length of the antenna 110.However, a method of tuning the length of the antenna according to thepresent exemplary embodiment should be performed by the tuning of a moldof the antenna 110. Therefore, the small antenna apparatus according tothe exemplary embodiment may vary at least one of the electric circuits120 and 130 in order to increase an electrical length to the samephysical length of the antenna 110, thereby making it possible to movethe resonance frequency. Therefore, the small antenna apparatus,according to the present exemplary embodiment, may increase theelectrical length while reducing the length of the antenna 110 by usingat least one of the electric circuits 120, 130 and 140, such that thesize of the antenna apparatus may be further reduced. In addition, theresonance frequency of the antenna apparatus may be easily changed bycontrolling at least one of the electric circuits 120, 130, and 140.

To this end, the PIFA, according to the present exemplary embodiment,may connect the electric circuits 120 and 130 to both ends ofasymmetrical antenna pattern 110 that is printed on the PCB. Here, theelectric circuits 120 and 130 may allow for a decrease in the physicallength of the antenna 110 by improving the input impedance whileincreasing the electrical wavelength of the antenna apparatus. In thiscase, the electric circuits 120 and 130 may be implemented on the PCB150. In addition, in the present exemplary embodiment, the electriccircuit 140 for improving the input impedance may be inserted betweenthe antenna 110 and the feeding line. Here, the electric circuits 120,130 and 140 may be an inter-digital circuit, a lumped element, a chipelement, or any other suitable and/or similar electric circuit. That is,the electric circuits 120, 130 and 140 may be configured to include aninductor L, a capacitor C, or a combination of the inductor L and thecapacitor C, a circuit configured of a diode, a FET, and a BJT that areactive devices, and/or a circuit configured of a combination of RFpassive and active devices or a combination of the inter-digitalcircuits, and/or any other suitable and/or similar circuit elements.

In the PIFA of the exemplary embodiment of FIG. 1, the electric circuit120 connected between the shorting point and the antenna 110 uses acapacitor. The electric circuit 130 connected between the antenna 110has the largest energy and uses an inductor. A case in which theinter-digital circuit is used between the FP and the antenna 110 isshown in FIG. 1.

FIG. 2 is diagram illustrating a configuration of an equivalent circuitof a small antenna having a configuration such as the configurationshown in FIG. 1 according to an exemplary embodiment of the presentinvention.

Referring to FIG. 2, the resonance of the antenna apparatus may be mostaffected by the physical length of the antenna 110. Since the change ofthe length of the antenna 110 may cause a change in an inductor L_(A), acapacitor C_(A), and a resistor R_(A), the resonance may generated at aspecific frequency. The physical length of the resonance in the generalPIFA is a ¼ wavelength. In the present exemplary embodiment, theelectric circuit 140 may vary the input matching because it is connectedto the feeding line of the antenna 110. Each of the electric circuits120 and 130 may be disposed at both ends of the antenna pattern 110,which includes the inductor L_(A), the capacitor C_(A), and the resistorR_(A), to compensate the change of the physical length, thereby makingit possible to have the resonance frequency be at a specific frequency.At this time, an equivalent circuit model of FIG. 2 shows that theelectric circuit 140 may include a capacitor Cp and each of electriccircuits 120 and 130 include a capacitor Cs and an inductor Ls.

The electric circuit 140 in the small antenna apparatus may match theinput impedance of the feeding line. In addition, the electric circuits120 and 130, which are positioned at both sides of the antenna 110, mayreduce the size of the ground and the length of the antenna 110. Theelectric circuit 120 may perform the function matching the inputimpedance of the antenna 110. Therefore, in the small antenna apparatus,according to the present exemplary embodiment, having the configurationas described above, the electric circuits 120 to 140 may be connected toboth ends of the antenna 110 and a feeding line, such that theelectrical wavelength and the input impedance may be simultaneouslyimproved. Although FIG. 2 shows that both the electric circuit 120 and130 are implemented as variable electric circuit, the present inventionis not limited thereto, and only one of the electric circuits 120 and130 may be implemented as variable electric circuit.

FIG. 3 is a diagram illustrating a flow of current in an antenna at atime of resonance generation in a small antenna apparatus according toan exemplary embodiment of the present invention.

Referring to FIG. 3, when the current is supplied into the FP, thecurrent may be introduced to the antenna 110 through the feeding lineand electric circuit 140 and the current flowing through the antenna 110has a largest energy and is radiated in the electric circuit 130. Inaddition, the antenna apparatus forms a transmission line circulatingthe antenna 110, the electric circuit 130, the system ground of the PCB150, and the electric circuit 120 by the current supplied to the FP.Accordingly, the resonance frequency, as determined by the length of theantenna 110 and the electric circuits 120 and 130, may be generated. Atthis time, as shown in FIG. 3, a maximum energy is discharged at an endportion of the antenna 110 of the antenna apparatus.

FIG. 3 shows a flow of electricity when tuning of electric circuits iscompleted after fixing a length of an antenna, and shows that resonancepoint tuning through an electric circuit may be performed according toan exemplary embodiment of the present invention. Accordingly, the smallantenna apparatus, according to the present exemplary embodiment, maychange the resonance frequency using the electric circuit, such as theelectric circuits 120, 130 and 140, other than the physical length ofthe antenna 110. Thus, there may be no need to modify the mold due to apattern correction of the antenna 110 not being necessary.

FIG. 4 is a diagram illustrating a structure of a small antenna havinganother structure printed on a PCB according to an exemplary embodimentof the present invention.

Referring to FIG. 4, another structure of the PIFA is shown. Theelectric circuits 120 and 130 may be connected to the both ends of theantenna 110 and the PCB 450. A feeding line connected to the FP isconnected to an antenna 410 through an electric circuit 140. Here, theconfigurations are the same as the PIFA structure of FIG. 1 except thatthe electric circuit 120 is configured by an inter-digital circuit. Theinter-digital circuit may have a parasitic parameter smaller than a chipinductor and the capacitor. Thus, it may be manufactured with a lowtolerance. Therefore, when the inter-digital circuit is used, the tuningof the frequency may be more accurately performed than when the chipcircuit is used, in the same environment. The parasitic parameter may bereduced to have a wide bandwidth, thereby making it possible to reduce amanufacturing cost. Generally, the shorting point of the antenna 110 hasa characteristic that the frequency may be significantly changed evenfor a change of a fine value. The electric circuit 120 connected to theshorting point of the antenna 110 may use the inter-digital structure.

FIG. 5 is a diagram illustrating a structure of a small antenna having aconfiguration of an antenna apparatus when an antenna is attached to aspecific tool of the mobile terminal according to an exemplaryembodiment of the present invention.

Referring to FIG. 5, although the antenna 110 is shown with a form whichis horizontally symmetrical, the present invention is not limitedthereto, and the antenna 110 and may be formed as an appropriateasymmetrical antenna according to characteristics of tool disposition.

The antenna 110, which may be formed of a metal conductor, may beattached to a specific tool of the apparatus, which may be a mobileterminal Both ends of the antenna 110 are connected to the PCB through apad 550 and 555, respectively. In addition, the electric circuit 120 isconnected to the pad 550 and the electric circuits 140 and 130 areconnected to the pad 555. In addition, each of the other ends of theelectric circuits 120 and 130 is connected to the system ground and theother end of the electric circuit 140 is connected to the FP. As shownin FIG. 5, the antenna apparatus has a structure in which the antenna110 is attached to the specific tool and both ends of the antenna 110are connected to the electric circuits 120, 130 and 140 positioned onthe PCB through the pad 550 and 555.

As shown in FIG. 5, the antenna 110 may be a conductor made of a metalmaterial and may be manufactured according to the space characteristicsof the tool. That is, the antenna 110 may be configured as a patternhaving a symmetric or an asymmetric form as the metal material and maybe formed in the appropriate form according to the space characteristicsof the tool in the apparatus. Further, both ends of the antenna 110 areconnected to the PCB through the pads 550 and 555. As shown in FIGS. 1and 4, the PCB may extend the electrical length of the antenna and mayinclude the electric circuits 120, 130 and 140, which may match theinput impedance of the antenna 110. The electric circuits 120, 130, and140 are connected to the antenna 110 through the pads 550 and 555.Therefore, the antenna apparatus may have a structure in which theantenna 110 is attached to the specific tool and to the circuit atrespective sides of the antenna 110 and the feeding line of the antenna110 is shorted by the electric circuits 120, 130 and 140 that areconnected to the PCB.

The antenna apparatus may be formed in a manner similar to that of theantenna apparatus of FIG. 1. An equivalent circuit of the antennaapparatus having the configurations shown in FIGS. 4 and 5 has theconfiguration as shown in FIG. 2. The flow of current at the time of theresonance generation has the flow as shown in FIG. 3.

As shown in FIGS. 1, 4, and 5, the antenna apparatus, according to thepresent exemplary embodiment, is not limited by a shape of the antennapattern or a position on the PCB, on a carrier, or the outside tool of amobile phone, or the like, at which the antenna apparatus is disposed.The change of the characteristics such as a movement of the resonancegenerating point due to a difference of a dielectric constant may beeasily solved by tuning of the electric circuit. The electric circuit120 in FIGS. 1, 4, and 5 may be a first electric circuit, the electriccircuit 130 may be a second electric circuit, and the electric circuit140 may be a third electric circuit. In FIG. 5, the pads 550 and 555 area pad in which the antenna 110 and the PCB are connected to each other.The pad 550 may be a first pad and the pad 555 may be a second pad.

FIG. 6 is a diagram illustrating a small antenna apparatus in whichinput impedance and a length of an antenna are matched to each other byconnecting an electric circuit to both ends and a feeding ends of anantenna according to an exemplary embodiment of the present invention.The FIG. 6 illustrates the antenna apparatus in the PIFA structure.

Referring to FIG. 6, the antenna of the PIFA type may be implemented inthe size of 8 mm*4.5 mm in the PCB having a dielectric constant of 4.4,a thickness of 0.8 mm, and a size of 70 mm*40 mm. In addition, both endsof the antenna of the PIFA type are connected to the electric circuit,which may be a lumped element and inter-digital structure. Here, theantenna apparatus of FIG. 6 illustrates that a capacitor is connected toa shorting point of the antenna 110 and an inductor is connected to theother end having the maximum energy of the antenna 110 when the electriccircuit is connected to the antenna apparatus. Also, a meander linelength L is shown. In this case, when an inductance and a capacitanceare increased, the antenna apparatus may use circuit resonance insteadof wave resonance, such that the resonance frequency moves to a lowfrequency band. Accordingly, the inductance and the capacitance may varythe operating frequency of the antenna 110. Hence, performance of theantenna 110 may be improved.

FIGS. 7A and 7B are diagrams illustrating change characteristics of aresonance point due to a change of an electric circuit connected to bothends of an antenna in an antenna apparatus having a structure such asthat shown in FIG. 6 according to an exemplary embodiment of the presentinvention.

Referring to FIG. 7A, change characteristics of return loss of theantenna due to the change of inductance are illustrated. Referring toFIG. 7B, change characteristics of return loss of the antenna due to thechange of capacitance are illustrated. The change characteristicsillustrated in FIGS. 7A and 7B may acquire an optimum return loss in theinductance of 2.0 nH and the capacitance of 0.6 pF, respectively.

FIG. 8 is a diagram illustrating change characteristics of return lossdue to a change of an electric circuit connected to a FP of an antennaapparatus having a structure such as that shown in FIG. 6 according toan exemplary embodiment of the present invention.

Referring to FIG. 8, the electric circuit of the FP uses theinter-digital structure. The inter-digital structure affects the inputimpedance and operating frequency of the antenna. At this time, when ameander line length L (see FIG. 6) is increased, the impedance alsoincreases due to the inter-digital structure. In FIG. 8, in a case wherethe meander line length L is 0.8 mm long, good impedance matching of aninput port may be achieved.

As shown in FIGS. 7A and 7B, when the pattern of the antenna 110 isfixed, the shorted electric circuits 120 and 130 are connected to bothends of the antenna 110, and the device values, i.e. characteristics, ofthe electric circuits 120 and 130 are changed, it may be appreciatedthat the resonance point of the antenna 110 is changed. As shown in FIG.8, when the device value of the electric circuit 140, which is connectedto the feeding line, is changed, then the return loss of the resonancefrequency adjusted by the electric circuits 120 and 140, which areconnected to both ends of the antenna 110, may also be increased.

FIG. 9 is a diagram illustrating a configuration of changing an electriccircuit in an antenna apparatus according to an exemplary embodiment ofthe present invention according to an exemplary embodiment of thepresent invention, and FIG. 10 is a flowchart illustrating a procedureof changing an electric circuit of an antenna apparatus such as thatshown in FIG. 9 according to an exemplary embodiment of the presentinvention.

Referring to FIGS. 9 and 10, a measuring apparatus 900 measuresoperations of each portion of the antenna apparatus and the antennaapparatus may have the configuration such as those shown in FIG. 1, 4 or5. In the present exemplary embodiment of FIG. 9, the antenna apparatushas the configuration as shown in FIG. 4.

First, the measuring apparatus 900 provides feedback of at least onesignal from among signals of a position proximate to each of theelectric circuits 120, 130, and 140 of the antenna apparatus in order todetermine an optimum frequency channel or calibration of process. Atthis time, the position at which the measuring apparatus 900 inputs thefeedback signal may be a position 911 of the antenna 110 close to theelectric circuit 120 connected between the shorting point and antenna110, a position 915 of the antenna 110 close to the electric circuit 130positioned at an end of the antenna 110, and/or a position 913 of thefeeding line between the electric circuit 140 and feeding point. Themeasuring apparatus 900 inputting the feedback signal of at least one ofthe positions 911, 913 and 915 measures RF parameters, such as TotalIsotropic Sensitivity (TIS), Total Radiated Power (TRP), Bit-Error-Rate(BER), gain, efficiency, and other similar and/or suitable RFparameters, using the feedback signal. At this time, the measuringapparatus 900 stores a reference value of a preset RF parameter andcompares the measured RF parameter with the reference value. When thecomparison result is not the set frequency, i.e. a spec out occurs whichhappens when the result is outside of the specification, the measuringapparatus 900 changes the device value of at least one of the electriccircuits 120, 130 and 140 in order to change the resonance frequency.

In other words, and while referring to FIG. 10, after inputting thefeedback signal of at least one of the positions 911, 913, and 915, themeasuring apparatus 900 measures the RF parameter of the feedback signalat operation 1011. Thereafter, the measuring apparatus compares themeasured RF parameter with a preset reference RF parameter at operation1013. In this time, when the antenna apparatus generates a resonancefrequency deviating from a set specification, i.e., the spec out eventoccurs, then the measuring apparatus 900 senses it the deviation of theresonance frequency at operation 1013, and changes at least one of theelectric circuits 120, 130 and 140 at operation 1015. The operations1011, 1013, and 1015 may be repeated until the antenna apparatusgenerates the resonance frequency within the set specification.Moreover, when the antenna apparatus generates the resonance frequencywithin the set specification, i.e. a spec in event occurs, at operation1013, then the measuring apparatus 900 returns to operation 1011 withoutperforming the adjustment operation 1015 that is for the changing of theelectric circuits 120, 130 and 140. As discussed, above, the smallantenna apparatus having the configurations shown in FIGS. 1, 4, and 5may be mounted in the mobile terminal.

FIG. 11 is a diagram illustrating a configuration of a mobile terminalin which a small antenna apparatus according to an exemplary embodimentof the present invention.

Referring to FIG. 11, an antenna apparatus 1100 may have theconfiguration such as that shown in FIGS. 1, 4, and 5. That is, theantenna apparatus 1100 has a structure in which each of the electriccircuits 120, 130 and 140 are connected to both ends of the antennapattern and/or the feeding line to which signal is supplied. The antenna1100 may be an antenna pattern implemented on the PCB 150 or an antennapattern of the metal material attached to the tool. Further, the antenna1100 may be asymmetrically formed based on the feeding line for freemounting. The electric circuits 120, 130 and 140 may be circuitsincluding an electric device such as a passive device and an activedevice for generating electrical resonance. The electric device may beimplemented as a chip type, a package type or an inter-digital structureimplemented on the PCB.

In addition, the antenna apparatus 1100 receives and transmits afrequency of set bandwidth. Accordingly, the antenna apparatus 1100 maybe an antenna for communication networks such as an LTE network, a WCDMAnetwork, a Global System for Mobile communications (GSM) network, andany other similar and/or suitable communication network type, in thecase of antenna communicating with a base station, an antenna forcommunication networks such as a WiFi network, a Wibro network, and anyother similar and/or suitable communication network type, in the case ofantenna for communicating with the Internet network, or an antenna forcommunication networks such as an NFC network, a Bluetooth network, andany other similar and/or suitable communication network type, in thecase of antenna communicating for near field communication. In thepresent exemplary embodiment, for convenience of explanation, it isassumed that the antenna apparatus 1100 is an antenna for base stationcommunication. In this case, the antenna apparatus 1100 may be connectedto a base station communication unit 1130. However, when the antennaapparatus 1100 is not the antenna for base station communication, thenthe antenna apparatus 1100 is not connected to the base stationcommunication unit 1130.

The communication unit 1130 performs a wireless communication with thebase station. Here, the communication unit 1130 may include atransmission unit for up-converting a frequency of a transmission signaland for amplifying a power and may also include a reception unit forlow-noise amplifying a received signal and down-converting a frequencyof the received signal. In addition, the communication unit 1130 mayinclude a modulator and a demodulator. Here, the modulator modulates thetransmission signal and transfers it to the transmission unit. Thedemodulator demodulates the signal received through the reception unit.In this case, the modulator/demodulator may be for any type ofcommunication network.

A control unit 1110 controls the overall operation of the mobileterminal. According to the present exemplary embodiment, the controlunit 1110 confirms an RF parameter transmitted from the base station andchanges the device value of the electric circuit of the antennaapparatus 1100 when the RF parameter is not a reference RF parameter.

A memory 1120 may include a program memory that stores an OperatingSystem (OS) program of the terminal and a program according to theexemplary embodiments of the present invention as well as any othersimilar and/or suitable programs for the mobile terminal, and a datamemory that stores tables for operation of the mobile terminal and datagenerated when performing a program. Particularly, the memory 1120 mayinclude a change table that stores a reference RF parameter of thepresent invention and a control data for changing the device value ofthe electric circuit of the antenna apparatus 1100.

In addition, the control unit 1110 may control the device value in anactive type which gradually changes the device value until it satisfiesa specification, which is the reference value, due to characteristics ofthe wireless channel that does not have noise or a predeterminedpattern. In this case, the memory 1120 does not include the changetable. That is, when changing the device value of electric circuit ofthe antenna apparatus 1100, the control unit 1110 may use a first methodof using a device value change table of the memory 1120. In addition, itmay use a second method of determining a value satisfying thespecification by gradually changing the device value without use of thedevice value change table.

A display unit 1150 may be any suitable display device, such as a LiquidCrystal Display (LCD) or an Organic Light Emitting Diode (OLED) displaypanel, for displaying the data, an image, and the like, that may begenerated when performing operations of the programs under the controlof the control unit 1110. An input unit 1140, which is a touch panel,senses a touch input of a user and transfers it to the control unit1110. However, the present invention is not limited thereto, and theinput unit 1140 may be the touch panel or any other similar and/orsuitable input device. Here, the input unit 1140 and the display unit1150 may be all-in-one touch screen.

The mobile terminal having the configuration of the present exemplaryembodiment receives the RF parameter from the base station and changesthe device value of at least one of the electric circuits 120, 130, and140 of the antenna apparatus 1100, thereby making it possible to adjustthe resonance frequency. That is, when the mobile terminal is calibratedin a manufacturing process and mounted in the mobile terminal, thefrequency resonance value of the antenna apparatus may be changed byexternal and internal environments. In this case, the antenna apparatus1100 of the present of the present exemplary embodiment may change thedevice value of the internal electric circuits 120, 130 and 140 and maygenerate a desired resonance frequency. At this time, the mobileterminal may change the resonance frequency of the antenna apparatus1100 using the signal received from the base station. In addition, themobile terminal may measure an output of the antenna apparatus 1100 byitself, such that the resonance frequency of the antenna apparatus 1100may be changed.

In the case of the first method, the base station measures the RFparameter such as TIS, TRP, BER, gain, efficiency, or the like from thesignal transmitted from the mobile terminal and transmits it to themobile terminal so as to change the frequency of the antenna in order tosearch the optimal frequency channel. In addition, the mobile terminalcompares the reference RF parameter stored in the memory 1120 with thereceived RF parameter in order to change the electric circuit of theantenna apparatus 1100 when needed, such that the resonance frequency ofthe antenna apparatus 1100 is changed. In the case of the second method,as shown in FIG. 9, the control unit 1110 of the mobile terminalmeasures a feedback signal in each position 911, 913 and 915 of theantenna apparatus 1100 in order to obtain the RF parameter, and comparesit with the stored reference RF parameter in order to change theelectric circuit of the antenna apparatus 1100.

FIG. 12 is a flowchart illustrating a procedure of changing a resonancefrequency of an antenna apparatus in a mobile terminal according to anexemplary embodiment of the present invention.

Referring to FIG. 12, the resonance characteristic of the antennaapparatus 1100 is shown to be changed by receiving the RF parameter fromthe base station. When the RF parameter is received from the basestation, the control unit 1110 senses it at operation 1211, and comparesthe reference RF parameter stored in the memory 1120 with the receivedRF parameter at step 1213. Here, when the received RF parameter deviatesfrom a range of the set reference parameter, i.e., the spec out occurs,and then the control unit 1110 senses it at operation 1213. Afteraccessing corresponding change data in the change table of the memory1120 at operation 1215, the control unit 1110 changes a correspondingdevice value of the electric circuit from among the electric circuits120, 130 and 140 of the antenna apparatus 1100 at operation 1217. Then,the antenna apparatus 1100 generates resonance with a frequency of theband set by the electric circuit having the changed device value.Additionally, at operation 1211, if no RF parameter is received, then acorresponding function is performed at operation 1221.

At this time, the change of the device value of the electric circuit ofthe antenna apparatus 1100 may be set in the electric circuits 120, 130and 140, two of the electric circuits 120 to 140, or any one of theelectric circuits 120, 130 and 140. In addition, the change table of thememory 1120 may store the device change value of the set electriccircuit corresponding to the difference of the reference RF parameterand the received RF parameter. Therefore, when the device value of theelectric circuits 120, 130 and 140 is changed at operation 1215, thecontrol unit 1110 determines a difference value between the reference RFparameter and the received RF parameter, and retrieves the device valueof the electric circuit of the change table corresponding to thecalculated difference value in order to change a corresponding devicevalue of the electric circuit of the antenna apparatus 1100.

As described above, the memory 1120 may not include the device valuechange table. In this case, when a comparison value of two parametersdeviates from the reference specification, the control unit 1110 changesthe device value of the electric circuit of the antenna apparatus 1100.At this time, the control unit 1110 may change the corresponding devicevalue of the electric circuit of the antenna apparatus 1100 until thespecification of the reference RF parameter is satisfied. That is, thecontrol unit 1110 may set the change value in a passive type electronicdevice by previously setting the change value, or gradually may changethe device value in an active type electronic device until thespecification, which is a reference value, is satisfied due tocharacteristics of the wireless channel that does not have noise or apredetermined pattern. That is, the control unit 1110 may use a devicevalue change table. On the other hand, when the device value changetable does not exist, it may search a value satisfying the spec bygradually changing the value.

As discussed above, FIG. 12 illustrates an operation procedure forreceiving the RF parameter from the base station. However, as shown inFIG. 9, the control unit 1110 may feedback an output of the antennaapparatus 1100 in order to measure the RF parameter. In this case, thecontrol unit 1110 provides feedback of the output of the antennaapparatus 1100 in order to measure the RF parameter at operation 1211,and then compares it with the stored reference RF parameter at operation1213. Then, after operation 1213, the remaining the remaining operations1215 and 1217 may be performed as described above.

The small antenna apparatus according to the exemplary embodimentsdiscussed above has antenna pattern provided in the PCB or tool,connects the electric circuit, which may be at least one of or acombination of an active device and a passive device, on the PCB to thefeeding line and to both ends of the antenna, such that the size of theantenna is reduced so as to efficiently utilize the space. Furthermore,a circuit resonance type operation may be used to perform the tuning ofthe electric circuit connected at the time of changing the resonancepoint, such that the antenna resonance frequency may be efficientlychanged. Accordingly, the antenna apparatus according to the exemplaryembodiments discussed above may reduce the antenna mounting space so asto provide a multi-function such that the antenna apparatus may beefficiently applied to the mobile terminal performing various wirelesscommunication functions. In addition, at the time of changing theresonance point, not by using a physical length change of the antennathrough the mold, but by tuning the connected electric circuit, thedevelopment time and cost of the mobile terminal may be reduced.

While the invention has been shown and described with reference tocertain exemplary embodiments thereof, it will be understood thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims and their equivalents.

What is claimed is:
 1. An antenna apparatus, comprising: an antennapattern; a first electric circuit and a second electric circuitrespectively connected between both ends of the antenna pattern and asystem ground; and a third electric circuit disposed between the antennapattern and a feeding line, wherein the first electric circuit, thesecond electric circuit, and the third electric circuit extendelectrical wavelengths of the antenna pattern in order to increase aninput impedance matching.
 2. The antenna apparatus of claim 1, whereinthe antenna pattern is asymmetrically formed based on the feeding line.3. The antenna apparatus of claim 1, wherein the first electric circuit,the second electric circuit, and the third electric circuit include atleast one of a passive device, an active device, and a combination ofthe passive device and active device.
 4. The antenna apparatus of claim3, wherein the device has at least one of a chip type structure, apackage type structure, and an inter-digital structure.
 5. The antennaapparatus of claim 4, wherein the first electric circuit is a capacitorconnected between a shorting point and an end of the antenna pattern,wherein the second electric circuit is a capacitor connected betweenanother end of the antenna pattern and the system ground, and whereinthe third electric circuit has the inter-digital structure.
 6. Theantenna apparatus of claim 1, wherein the antenna apparatus is a planarinverted-F antenna.
 7. The antenna apparatus of claim 1, wherein theantenna pattern is formed of a metal material, wherein an end of theantenna pattern is connected to the first electric circuit through afirst pad of a Printed Circuit Board (PCB), and wherein another end ofthe antenna pattern is connected to the second electric circuit and thethird electric circuit through a second pad of the PCB.
 8. A mobileterminal comprising: an antenna apparatus comprising: an antennapattern; a first electric circuit and a second electric circuitrespectively connected between both ends of the antenna pattern and asystem ground; and a third electric circuit disposed between the antennapattern and a feeding line; a communication unit for receiving a RadioFrequency (RF) parameter from a base station; a memory for storing areference RF parameter therein; and a control unit for comparing thereceived RF parameter with the reference RF parameter and for changing adevice value of a corresponding electric circuit, from among the firstelectric circuit, the second electric circuit and the third electriccircuit, of the antenna apparatus until a comparison value between thereceived RF parameter and the reference RF parameter satisfies areference specification when the comparison value is not the referencespecification.
 9. The antenna apparatus of claim 8, wherein the antennaapparatus is a planar inverted-F antenna.
 10. The antenna apparatus ofclaim 8, wherein the antenna pattern is formed of a metal material,wherein the end of the antenna pattern is connected to the firstelectric circuit through a first pad of the PCB, and wherein the otherend of the antenna pattern is connected to the second electric circuitand the third electric circuit through a second pad of the PCB.
 11. Amobile terminal comprising: an antenna apparatus comprising: an antennapattern; a first electric circuit and a second electric circuitrespectively connected between both ends of the antenna pattern and asystem ground; and a third electric circuit disposed between the antennapattern and a feeding line; a memory for storing a reference RFparameter therein; and a control unit for measuring an RF parameterwhich is outputted from the antenna apparatus, for comparing themeasured RF parameter with the reference RF parameter, and for changinga device value of a corresponding electric circuit, from among the firstelectric circuit, the second electric circuit and the third electriccircuit, of the antenna apparatus until a comparison value between themeasured RF parameter and the reference RF parameter satisfies areference specification when the comparison value is not the referencespecification.
 12. The antenna apparatus of claim 11, wherein theantenna apparatus is a planar inverted-F antenna.
 13. The antennaapparatus of claim 11, wherein the antenna pattern is formed of a metalmaterial, wherein an end of the antenna pattern is connected to thefirst electric circuit through a first pad of the PCB, and whereinanother end of the antenna pattern is connected to the second electriccircuit and the third electric circuit through a second pad of the PCB.14. A method for controlling a resonance frequency of an antenna of amobile terminal, the method comprising: receiving a Radio Frequency (RF)parameter from a base station; comparing the received RF parameter witha reference RF parameter stored in a memory of the mobile terminal; andchanging a device value of a corresponding electric circuit of anantenna apparatus until a comparison value between the received RFparameter and the reference RF parameter satisfies a referencespecification when the comparison value is not the referencespecification, wherein the antenna apparatus includes an antennapattern, a first electric circuit and a second electric circuitrespectively connected between both ends of the antenna pattern and asystem ground, and a third electric circuit disposed between the antennapattern and a feeding line.
 15. A method for controlling a resonancefrequency of an antenna of a mobile terminal, the method comprising:measuring an output of an antenna apparatus including an antennapattern, a first electric circuit and a second electric circuitrespectively connected between both ends of the antenna pattern and asystem ground, and a third electric circuit disposed between the antennapattern and a feeding line; comparing the measured RF parameter with areference RF parameter; and changing a device value of a correspondingelectric circuit of the antenna apparatus until a comparison valuebetween the measured RF parameter and the reference RF parametersatisfies a reference specification when the comparison value is not thereference specification.